As Barack Obama prepares to issue an Executive Order to close the Guantanamo Bay military prison the Pentagon reports a rise in the number of detainees who rejoined terrorist missions after being released.

The Department of Defense says that the number of Guantanamo prisoners—all suspected Middle Eastern terrorists—who have returned to “the fight” since their release from custody has nearly doubled in a short time from 37 to 61.

The information was revealed this week by the Pentagon’s Defense Intelligence Agency, which gathers foreign military intelligence. The agency used data such as fingerprints, pictures and other intelligence reports to confirm the high rate of recidivism among released prisoners.

About 255 suspected terrorists—all men—are still imprisoned at the U.S. naval base in Cuba and Obama has vowed to issue an order to close it during his first week as president. About 500 prisoners have been freed or transferred to other countries since 2002 and defense officials say scores of detainees should never be released because they pose a serious threat to the United States.